Precessional device and method

ABSTRACT

A precessional device having independent control of the output torque generated by the device and the oscillation rate of the device is disclosed. The device comprises a rotor supported by an axle wherein the ends of the axle are supported by a circular race. The circular race is rotatable, and may be driven by a motor or other means, thereby controlling the oscillation rate of the device independently of the output torque arising from the rotation rate of the rotor. The motor may be controlled by a control program that adjusts the rotation rate of the circular race to modify the shape of the resistance curve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior application Ser. No.10/428,761 entitled “Precessional Device and Method” and filed 02 May2003, which is incorporated in its entirety by this reference.

FIELD OF THE INVENTION

The present invention relates to precessional devices. Morespecifically, the invention relates to a device and method which utilizeprecessional forces in a controlled manner.

BACKGROUND

Most existing precessional devices are passive devices that require adeflecting torque from an external source to generate a precessionaltorque. A common example of this type of precessional device is thegyroscopic heading indicator used for aviation navigation. The spinningrotor inside such a device does not generate precessional torque on itsown, rather, it simply responds to the torque exerted on it (by thedirectional changes of the aircraft) by maintaining its original headingrelative to the magnetic compass.

In contrast to this passive type of precessional device, U.S. Pat. No.6,401,556 issued to Hamady on Jun. 11, 2002, herein incorporated byreference in its entirety, discloses a precessional device whichgenerates a precessional torque without requiring an externally inputteddeflecting torque. The disclosed device employs rotors which precessalong a circular race or track. Axles run through each rotor makingcontact at either end with the surface of the tracks. The rotors' spinrate, ω_(s), is directly proportional to the rotational velocity, ω_(r),which is defined as the frequency of the rotors' precession around thetrack. The relationship between ω_(r) and ω_(s) is determined by theratio of the diameter of the axle tips such that ω_(s)=ω_(r)d_(track)/d_(axle). The practical implication of this directrelationship is that the rotor speed (and resulting net precessionaloutput torque) can not be increased without a corresponding increase inthe oscillation frequency (Hz) of the net output torque. This limits thedevices usefulness in applications such as resistive exercise where highresistance is often associated with slower movements and low resistanceexercise is often associated with faster movements. Therefore, thereremains a need for a device where ω_(s) may be increased beyond theconstraints defined by ω_(s)=ω_(r) d_(track)/d_(axle), including but notlimited to, a device where ω_(s) and ω_(r) may be controlledindependently of each other.

SUMMARY OF THE INVENTION

One embodiment of the present invention is directed to an apparatuscomprising: a rotor spinning at a rotor spin rate about a spin axis; anaxle supporting the rotor, the axle having a first axle tip, a secondaxle tip, and a longitudinal axis aligned with the spin axis of therotor; a rotatable circular race in rolling contact with the first axletip and in rolling contact with the second axle tip at a point on thecircular race diametrically opposite the first axle tip; a motor forrotating the circular race; and a controller for controlling therotation of the circular race independently of the rotor spin rate.

Another embodiment of the present invention is directed to an apparatuscomprising: a rotor spinning about a rotor axle at a rotor spin rate; atrack assembly in rolling contact with the rotor axle duringprecessional movement of the rotor; and means for rotating the trackassembly independently of the rotor spin rate.

Another embodiment of the present invention is directed to an apparatuscomprising: a first rotor spinning about a first spin axis and rotatingabout a first rotational axis inside a first rotatable track assembly,the first track assembly having a first tract rotation axis coincidentwith the first rotational axis; a second rotor spinning about a secondspin axis and rotating about a second rotational axis inside a secondrotatable track assembly the second track assembly having a second tractrotation axis coincident with the second rotational axis; and a housingsupporting the first rotatable track assembly and the second trackassembly, wherein neither spin axes are parallel to the rotational axes.

Another embodiment of the present invention is directed to a method formodifying a resistance curve characterized by a periodicity, theresistance curve generated by a precessional device, the methodcomprising: providing a precessional device comprising a rotor spinningat a spin frequency capable of precessional rotation at a precessionalfrequency in a track assembly; and rotating the track assembly to modifythe periodicity of the resistance curve.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be described by reference to the preferred andalternative embodiments thereof in conjunction with the drawings inwhich:

FIG. 1 is a perspective view of one embodiment of the present invention;

FIG. 2 is a section view of the axle and track assembly in anotherembodiment of the present invention;

FIG. 3 is a schematic diagram of the controller for the embodiment shownin FIG. 1;

FIG. 4 a is a perspective view of the embodiment shown in FIG. 1 housedin a hand-held exercise device;

FIG. 4 b is a perspective view of another embodiment of the presentinvention;

FIG. 5 is a graph illustrating a sinusoidal and modified resistancecurve generated by one embodiment of the present invention;

FIG. 6 a is perspective rendering illustrating another embodiment of thepresent invention;

FIG. 6 b is a side view rendering illustrating the embodiment shown inFIG. 6 a;

FIG. 6 c is a section view of a detail of the embodiment shown in FIGS.6 a and 6 b; and

FIG. 7 is a perspective view of another embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is an illustration of one embodiment of the present invention.The device illustrated in FIG. 1 includes two flywheel assemblies. Eachassembly 100 consists of a flywheel, or rotor 110, supported by an axle115 that extends at either end into a circular race or “track” 120.Bearing mounts 125 disposed toward each end of the axle 115 generate apreload that causes the flywheel/rotor assembly to cant at an angle, θ.In some embodiments, a motor 130 drives each track 120 through atransmission 140 that causes the tracks 120 to counter-rotate. The motor130 may be permanently attached to the device or may be external to thedevice and applied to rotate the tracks during the start-up of thedevice. Other means for driving the rotation of the tracks 120 such as,for example, manually rotating the tracks should be apparent to one ofskill in the art and are intended to be encompassed within the scope ofthe present invention. The motor 130 may be engaged to initially bringthe track rotation and rotor spin rate to an operational range anddisengaged once the track rotation and rotor spin rate are within theirrespective operational range. In the embodiment shown in FIG. 1, thetracks are vertically aligned or “stacked.”

A locking solenoid 150, when engaged to a lock plate 155, keeps theposition of the axle 115 fixed. The locking solenoid 150 and lock plate155 act as a clutch such that when the locking solenoid 150 is engagedwith the lock plate 155, the rotation of the motor driven track 120provides a driving force to increase or decrease the spin rate of therotor 110 about the rotor axis. Disengaging the locking solenoid 150from the lock plate 155, allows the spinning rotor 110 to rotate, orprecess, about the rotation axis of the rotatable track 120.

FIG. 2 is a section view of a detail of FIG. 1 showing the axle tipconfiguration in the circular race. Referring to FIG. 2, axle 115 issupported by bearing mount 125, which is supported by the axle tipsupport 210. The axle 115 is canted at an angle, θ, from horizontal suchthat the axle tip 225 is in rolling contact with the lower surface 230of the track 120. Although not shown in FIG. 2, the opposite end of theaxle 115 contacts the upper surface of the track 120. The profile of theaxle tip 225 is configured to allow rolling contact with the tracksurfaces 230 and is not limited by the exemplar profile shown in FIG. 2.In FIG. 2, the profile of the axle tip is cylindrical and is matched toan angled track surface that corresponds to the cant angle of the axle.Other profiles such as, for example, a tapered axle tip having a taperangle approximately the same as the cant angle of the axle may bematched to a horizontal, with respect to the orientation shown in FIG.2, track surface and should be understood to be encompassed within thescope of the present invention.

FIG. 3 is a schematic block diagram illustrating one embodiment of thecontroller for the precessional device. CPU 310 controls a user display312, user input devices such as, for example, a keypad 314 or usercontrols 316. Memory 318, such as for example, flash memory providesstorage for the control program and data structures executed by the CPU310. Audio or visual alarms, such as for example, a beeper 320 are alsocontrolled by the CPU 310 and provide feedback to the user. CPU 310provides power control 330 for the regenerative motor 130. The powersource for the motor may be supplied by batteries 332 in the device orby an external power supply 334. Retro-reflective opto-electronic sensor160, positioned on the axis of precession, provides the speed of eachrotor 110 to the CPU 310. An encoder within the track drive motor 130provides track speed data to the CPU 310. The current in the motor coilmay be measured via a current sensor such as, for example, a senseresistor and provided to the CPU 310. The current sensor may becalibrated by the control program executing on the CPU 310. Thedeflection angle indicating the angular position of the axle tip 225along the circumference of the track 120 is provided to the CPU 310 by asensor such as, for example, a piezoelectric gyro or goniometer.

The frictional contact between the moving track 120 and the axle tipscauses the flywheel 110 to rotate about the axle 115. In one embodiment,the rotor may accelerate to thousands of RPM as they are driven by thefrictional contact between the flywheel axle tips and the moving trackdriven by the motor 130. No precessional torque is generated during thespin-up of the flywheel, however, because travel of the tips within thetrack 120 is prevented by the engaged locking solenoid 150.

At a preset rotor speed sufficient to generate a noticeable outputtorque, the locking solenoid 150 disengages and current to the motor 130driving the tracks 120 is cut. When current is cut to the motor 130, themotor 130 acts as an electronic brake, braking the rotation of thetracks. In a preferred embodiment, the low transmission ratio from thetracks to the motor multiplies the braking effect of the motor therebyquickly stopping the rotating tracks. The rotational inertia of thespinning flywheel coupled by the frictional contact between axle tipsand track causes the rotor assembly to precess around the track.

The precession of the rotor assembly 100 around the track 120 acts as adeflecting torque on the spinning flywheel thereby generating aprecessional torque that is perpendicular to both the deflecting torqueand the axis of rotation. In the embodiment shown in FIG. 1, theprecessional torque generates a force that is normal to the surface ofthe track such that the axle tip is pressed into the surface of thetrack, as shown in FIG. 2. The combined, net torque generated by therotor assemblies, provides the resistive force that the user mustovercome. In other words, the operator exercises against this resistiveforce.

When the user inputs a deflecting torque against the rotor-generatedprecessional torque, causing the track surfaces to push back on the axletips, a second precessional torque is generated in the direction of therotation of the rotor assemblies. The second precessional torque causesan acceleration of the rotor assemblies around their respective tracks.The increased rotational velocity around the track, and thecorresponding increase in spin velocity, increases the rotor-generatedprecessional torque according to the formula τ=|ω_(s)ω_(r), where | isthe rotational inertia of the rotors, ω_(s) is the spin velocity of therotors, and ω_(r) is the rotational velocity of the rotor around thetrack.

The preferred range for spin velocity of the rotor depends on the sizeand mass of the rotor and on the desired torque output from the device.In some embodiments, the rotor spins at an operational angular speed ofbetween approximately 2,000-15,000 RPM, preferably between 4,000-12,000RPM, and most preferably between 8,000-10,000 RPM. In some embodiments,the precession of the axle tip in the circular race 120 is between about0.25-2.0 Hz. Once operational speed has been reached, the rotationalenergy of the rotor assemblies drives the tracks' counter-rotation. Thetrack motor continues to act as an electronic brake, siphoning energyout of the system to recharge the batteries.

FIG. 4 a is an illustration of one embodiment of the present invention.The precessional engine 410 may be packaged in a housing 420 that allowsfor safe and comfortable manipulation by a user. The housing 420provides secure support for the precessional engine 410 and transmitsthe internal forces generated by the precessional engine 410 through thedetachable outer handle 425 or other outer attachment accessories. Thedevice produces a smooth, harmonic oscillating net torque that can beused as the basis for resistive exercise including concentric andeccentric muscle exertions and aerobic and anaerobic exercises.

FIG. 4 b is an illustration of another embodiment of the presentinvention. The housing provides for ergonomically designed inputs 428for the user to control operations.

As previously described, the torque sensed by a user interacting withthe device is defined by: τ=|ω_(s)ω_(r), where | is the inertia of therotors (a function of their shape and mass), ω_(s) is the rotor spinvelocity (about the axis of the rotor axle) and ω_(r) is the rotationalvelocity of the rotor assemblies around the track. The rotationalvelocity, ω_(r), also referred to herein as the precessional velocity,determines the oscillation rate (Hz) of the net torque generated by thedevice.

In known precession devices, there is a fixed relationship, or ratio,between the rotor spin velocity, ω_(s), and the rotational velocity,ω_(r). The ratio, ω_(s)/ω_(r), may be determined by assuming purerolling of the axle tip on a fixed track surface, resulting in therelation, ω_(s)/ω_(r)=D_(t)D_(a), where D_(t) is the diameter of thetrack and D_(a) is the diameter of the axle tip. Both D_(t) and D_(a)are fixed and therefore ω_(s)/ω_(r) is also fixed once D_(t) and D_(a)are specified. Thus, in known precession devices, a given ω_(s)corresponds to a given ω_(r). An increase ω_(s) results in aproportional increase ω_(r). The user may increase ω_(r) by manipulatingthe device at a higher tempo, which increases the deflecting torque onthe rotors, causes an angular acceleration of the rotor assembliesaround the track, and produces a higher torque output, τ. The fixedratio of ω_(s)/ω_(r), however, requires an increase in ω_(r). Therefore,as the output torque is increased, the oscillation rate of the outputtorque must also increase. For the expected range of output torquesuseful in exercise devices, the oscillation rate is usually higher thanthe 0.5-1.5 Hz oscillation rate preferred for resistive exercise.

In contrast to the fixed relation between the output torque andoscillation rate of the output torque of prior art devices, the presentinvention allows independent control of the output torque andoscillation rate regardless of the ratio of the track diameter to theaxle diameter. The decoupling of the output torque from the oscillationrate of the present invention allows for a more compact precessionalengine that provides sufficient resistive exercise over a wider range ofresistive forces and oscillation rates.

In a preferred embodiment, the track 120 is rotatable and may becounter-rotated relative to the precession of the rotor.Counter-rotation of the track relative to the precession of the rotorallows for a greater effective rotor spin velocity with a smaller trackdiameter, allowing for more compact device designs than previouslyachievable. The relative precession rate, ω_(rp), is the rate ofrotation of the rotor assembly relative to the track surface and isgiven by ω_(rp)=ω_(r)+ω_(t), where ω_(t) is the rotation rate of thetrack. In the rotating track system, a relative precession rate of 4 Hz,for example, may be achieved as a combination of actual rotor assemblyrotation relative to the device as a whole ω_(r), and the rate of trackcounter-rotation ω_(t). For example, ω_(r) is 1 Hz and ω_(t) is 3 Hz,the relative precession rate, ω_(rp), is 4 Hz. The resulting outputtorque, τ, is 4 times greater than it would be if the track werestationary, since ω_(rp) is 4 times greater than ω_(r). The user maytherefore control torque output during operation by increasing ordecreasing the track counter-rotation rate, ω_(t).

FIG. 5 is a graph illustrating a resistance curve of one embodiment ofthe present invention. A typical resistance curve 510 is shown as asolid line in FIG. 5 and exhibits sinusoidal variation in the torque asa function of time. The sinusoidal variation arises from the precessionof the rotor assembly along the circumference of the track. In manyinstances, however, it is desirable to modify the shape of theresistance curve to other than a perfect sinusoid.

In some embodiments, the present invention allows for modification ofthe sinusoidal resistance curve 520 by computer control of the motorizedrotor, precession, and track speed. The sinusoidal resistance curve maybe modified by, for example, reducing the precession rate near the peakoutput, which flattens the force output and generates a more constantresistance force across each oscillation.

As an illustrative example, the track speed may be controlled on areal-time basis to accelerate track counter-rotation when the net torquecurve nears its peak. If the rotor spin rate, ω_(s), is constant, therelative precession rate, ω_(rp), will also remain constant. As thetrack rotation rate, ω_(t), is increased, ω_(r) must decrease in orderto maintain constant ω_(rp). As ω_(r) decreases, however, the outputtorque is also reduced thereby flattening the resistance curve.

Independent control of the track rotation may be used to quickly stopthe precession of the rotor assembly if the user loses control of thedevice. A pressure sensor may be disposed on the handle of the devicesuch that when the user breaks contact with the handle, a signal fromthe pressure sensor is transmitted to the CPU indicating loss of contactwith the handle. In response to the receipt of the signal from thepressure sensor, the control program may disengage the motor from thetrack, thereby allowing the track to free-wheel. The free-wheeling trackwill accelerate to match the precessional rotation rate, ω_(rp), suchthat ω_(r) quickly approaches zero. Alternatively, the motor may beengaged to counter-rotate the track such that the precession of therotor assembly is offset by the counter-rotation of the track.

FIG. 6 a is a rendering of another embodiment of the present invention.In the embodiment shown in FIG. 6 a, the motor 630 drives the rotationof the track assembly 620 via track drive shaft 638 and the rotorassembly 625 via rotor drive shaft 636. Rotor 610 and axle 615 spinsabout an axis coincident with the axle's longitudinal axis. The spinningaxle 615 is supported by rotor bearing 612, which is supported by therotor assembly 625.

FIG. 6 b is a side view of the embodiment shown in FIG. 6 a. The motordrive shaft 635 is connected through a series of drive belts to therotor drive shaft 636 and the track drive shaft 638. Transmission 640couples the rotor drive shaft 636 to the track drive shaft 638 such thatthe track drive shaft 638 counter-rotates to the rotor drive shaft 636.In addition, transmission 640 fixes the ratio between the track rotationfrequency and the rotor rotation frequency. The gear ratio of thetransmission may be changed to better suit the intended use of theprecessional engine.

FIG. 6 c is a section view of the axle and track assembly showing theaxle tip configuration in the circular track. Referring to FIG. 6 c,axle 615 is supported by rotor bearing 622, which is supported by therotor bearing mount 625. In the compact design shown in FIG. 6 c, thetrack 620 is supported by a housing—track bearing 640 that allows thetrack 620 to rotate relative to the housing chassis 650. The track 620is also coupled to the rotor bearing mount 625 through a track—rotorassembly bearing 645 that allows rotational movement of the track 620relative to the rotor bearing mount 625. The rotor bearing mount 625 issupported by a rotor assembly—housing bearing 647. In some embodiments,bearings 640, 645, and 647 are precision ring bearings that allow for alightweight but very powerful precessional engine. The embodiment shownin FIG. 6 c may be appropriate for specialized environments such as, forexample, high-end rehabilitation market at a relatively high cost. For abroader market segment, designs incorporating inexpensive bearings oralternative methods may be incorporated using design methods readilyavailable to one of skill in the art.

The configuration shown in FIG. 6 a, 6 b and 6 c show the trackassemblies having a coincident rotation axis. It should be understood,however, that the present invention is not limited to such aconfiguration. The vertical alignment of the track assemblies enables asingle motor to drive both track assemblies 620 and both rotorassemblies 625. Other embodiments within the scope of the presentinvention include, but are not limited to, multiple motors with eachmotor individually driving a single track or rotor assembly. When eachtrack or rotor assembly is driven by its own motor, a transmission isnot required and the rotation axes of the track assemblies may beparallel but not coincident.

The use of separate motors to drive the rotor and track assembliesallows independent control of ω_(s) and ω_(r) thereby allowingindependent control of the output torque and torque oscillationfrequency. The advantage of a single motor driving both the rotor andtrack assemblies through a transmission is reduced cost while stillallowing high output torque at a suitable oscillation frequency. For arotatable track, the relation between ω_(s) and ω_(r) is given byω_(s)=ω_(r) (1+G)(d_(track)/d_(axle)) where G is the ratio,G=ω_(t)/ω_(r). For prior art systems having a non-rotatable track,ω_(t)=0 and G=0. Counter-rotating the track results in a positive Gthereby generating a higher output torque at the same oscillationfrequency. Rotating the track in the same direction as the rotation ofthe spinning rotor results in a negative G thereby reducing the outputtorque at the same oscillation frequency.

FIG. 7 is a perspective view illustrating another embodiment of thepresent invention. A rotor 710 and axle 715 spin about a spin axis thatis coincident with the longitudinal axis of the axle 715. The tips ofthe axle 715 travel along the surface of a rotatable track assembly 720.The rotatable track assembly 720 is supported by a housing 750 thatallows the track to rotate in the housing 750. An external driving forcemay be applied to the rotor such that the rotor 710 and axle 715 beginto spin about the spin axis. The external driving force may be arotating motor shaft applied to the circumferential edge of the rotor orany mechanical or manual means for imparting a tangential force to thecircumferential edge of the rotor. A portion of the rotational energy ofthe spinning rotor 710 may be transferred to the track via thefrictional force of the spinning rotor tip against the track surface.The energy imparted by the spinning rotor may cause the track tocounter-rotate to the rotation direction of the spinning rotor. Aresistance force developed between the rotating track and housingreduces the rotation rate of the track thereby causing the rotorassembly to rotate in a direction opposite to the rotation of the track.

Having thus described at least illustrative embodiments of theinvention, various modifications and improvements will readily occur tothose skilled in the art and are intended to be within the scope of theinvention. Accordingly, the foregoing description is by way of exampleonly and is not intended as limiting. The invention is limited only asdefined in the following claims and the equivalents thereto.

1. An apparatus comprising: a track that rotates; and a rotor havingaxle tips that frictionally contacts the track as the rotor spins abouta spin axis at a spin rate and rotates about a rotational axis at arotation rate; wherein rotation of the track modifies a relativerotation rate of the rotor about the rotation axis independent of thespin rate of the rotor about the spin axis.
 2. The apparatus of claim 1,wherein the frictional contact between the axle tips and the trackdefines a relationship between the spin rate of the rotor about the spinaxis and the rotation rate of the rotor about the rotational axis.